"Is there a product that allows me to create a Victoria 4 clone from a Genesis 8 figure? There is such a product for Genesis 2 figures."'

Considering that OP does not own Poser, much of this information is over his head. But, to answer his question, yes, there is a DAZ product that can make Genesis 8 female accept V4 clothing. It is essentially creating a V4 clone capable of autofitting her clothing. Now, you can spend $30 for the product, or you can create your own V4 clone for free. There are instructions at the DAZ forum. I spent the evening generating my own V4 clone for G8F, and you can see my DS render below:

This is Genesis 8 Female sporting Aery Soul's Ive outfit for V4, a rather old item of clothing. It is autofitting the figure and will accept most morphs, within reason. It also poses well. Next, I will attempt to transfer morphs from V4 to G8F; I have found tutorial instructions explaining the process.